Photographic emulsion containing supersensitized pseudocyanines



March so, 1937. c E, K, MEES 2,075,047.

PHOTOGRAPHIC EMULSION CONTAINING SUPERSENS ITIZ'ED PSEUDOCYANINESOriginal Filed Nov. 4, 1932 Patented Mar. 30, 1937 PHOTOGRAPHIO EMULSIONCONTAINING SUPERSENSITIZEI) PSEUDOCYANINES Charles E. K. Mees,Rochester, N. Y., assignor, by

mesne assignments, to Eastman Kodak Company, Jersey City, N. J., acorporation of New Jersey Application November 4, 1932, Serial No.641,178 Renewed February 9, 1935 15 Claims.

This invention relates to sensitized photographic emulsions and moreparticularly relates to photographic emulsions such as those of thegelatino-silver-halide type containing a combination of sensitizers, oneof which cooperates with the other to sensitize the emulsion to a muchgreater degree than is possible with that sensitizer, or eithersensitizer alone, or even than would be evidenced by the sum total ofthe sensitization produced by the two separate sensitizers individually.

In other words, I have found that the sensitivity contributed tophotographic emulsions by certain sensitizers may be enhanced to a veryis considerable degree by adding to the basic sensitizer what I willterm a supersensitizer, the latter contributing to the emulsion thesensitivity which is peculiar to itself as well as activating orinducing further sensitivity in what I will term 20 the basicsensitizer. For example, a certain basic sensitizer may have a greenspeed of 50 H and D but when there is added thereto a supersensitizer,which may not even sensitize to the green at all (but to some otherportion of thegreen speed. Or, assuming the basic sensitizer tosensitize the emulsion to a green speed of 50 and the supersensitizer toseparately sensitize the 30 emulsion to a green speed of 5, the additionof thesupersensitizer to the basic sensitizer will sensitize theemulsion to a green speed beyond the sum total of the two separate greenspeeds, namely to a green speed, for instance of 80.

35 The combinations ofsensitizers and supersensitizers which are thesubject of the instant invention have the peculiar property that, inorder for the supersensitizer to increase the sensitivity of the basicsensitizer, the region of sensitivity of 40 the supersensitizer mustcoincide at least inpart with the region of sensitivity of the basicsensitizer. The unusual effects obtained by the combinations ofsensitizers which constitute the instant invention result, therefore,from the unusual in- 45 fluence or relation which the supersensitizershave upon or to the respective basic sensitizers.

Accordingly, it is among the objects of my invention to provide aphotographic emulsion which contains a basic sensitizer for the emul- 50sion and which also contains a supersensitizer which contributes its ownindividual sensitization to the emulsion and also increases thesensitization caused by the basic sensitizer. It is a further object ofmy invention to provide certain 55 combinations or mixtures ofsensitizers in a photographic emulsion which will contribute to theemulsion a sensitivity '(ability to respond to light) not heretoforeobtainable with either of the. individual sensitizers in thecombination. Other objects will become apparent to those skilled in theart upon a further perusal of this specification.

- I have found, for instance, that the sensitivity styryl compounds as asupersensitizer. I find this supersensitizing effect upon thesensitizing propertiesof pseudocyanines to be general with orrepresentative of certain styryl compounds, which themselves have theability of separately sensitizing photographic emulsions to some degree.

Referring to the attached drawing, forming a part hereof, there isrepresented a hypothetical wedge spectrogram illustrating .my invention.

The curve A shows the approximate sensitivity conferred upon agelatino-silver-halide emulsion by a pseudocyanine as a basicsensitizer. The curve B illustrates diagrammatically the sensitivityseparately conferred upon the same gelatino-silver-halide emulsion by astyryl compound. The curve C, however, illustrates the sensitivity ofthe same photographic emulsion containing a small percentage of asolution in which is dissolved approximately equal parts of thepseudocyanine and the styryl compound. From this it will be apparentthat the combination or mixture of these sensitizers contributes to thephotographic emulsion a sensitivity far beyond that which it is possibleto obtain even from the sum total of the sensitization resulting fromthe individual sensitizers.

More specifically my invention is accomplished by dissolving thesensitizing dyes in, for instance, methyl alcohol. The sensitizer andsupersensitizer are added to the alcohol, for instance, in equalproportions, although I have found that less than an equal amount of thesupersensitizer is normally sufficient to confer upon the sensitizer anincreased sensitvity. For example, while I may dissolve in the methylalcohol solvent one part of the pseudocyanine, I may then add to thealcohol from fith'part or even less of the styryl compound to one partor even more of the styryl compound, depending upon the effect that isdesired in the photographic emulsion. The exact ratio of thesupersensitizer to the sensitizer is not particularly important inasmuchas those skilled in the art can readily determine by what ratio thegreatest degree of sensitization of the basic sensitizer can beobtained.

This solution of the sensitizer and supersensitizer is then diluted withwater and a volume containing from a few milligrams to as much as 100milligrams, and preferably from about to 30 milligrams of thesensitizers, is then 10 added to 1000 cc. of a gelatino-silver-halideemulsion, such as is customarily employed in the art. Obviously, if thepseudocyanine is greatly supersensitized by the styryl compound, less ofthe sensitizer combination will be necessary to obtain the desireddegree of sensitization in the emulsion. The emulsion may then be coatedupon a transparent support, as is well known in the art, either glass,or cellulose nitrate or acetate, or other cellulose derivative,

0 base being satisfactory as the support.

As further illustrating my invention, I have tabulated hereinaftertypical examples of styryl compounds which themselves have the power ofsensitizing a photographic emulsion and also have the ability ofsupersensitizing the sensitizing effect of the pseudocyanine on thephotographic emulsion. Styryl compounds which are characteristic ofthose which I may employ as supersensitizers for pseudocyanines,opposite which they are set, are as follows l :2 diethylseleno-pseudocyanine iodide. 6 (6) methyl 1:1 diethyl pseudocyanineiodide 1:1 diethyl pseudocyanine iodide 1:1 diethyl psendocyanine iodide4 methyl 2 (p. diethyla- 4 phenyl 3 methyl 1 ethyl selenazolo mino)styryl thiazole pseudocyanine iodide ethiodide 4 phenyl 3 methyl 1 ethylselenazolo 1'22 diethylthiopseudocyanine iodide l:2 diethylpseudocyanine iodide 2 (pdlmethylamlno) y ryl thiazoline methiodide 2(p. dimethylamino) styryl benzothiazole ethiodide 2 (p. dimethylamino)styryl 6 ethoxy quinoline n-butiodide 2 (p. dimethylemino) styrylquinoline ethiodide 1'z2 diethyl pseudoeyenine iodide 0 1&2 dlethylpseudocyanine iodides.-.

122 diethylthiopseudocyenine iodide.-.

These examples illustrate a class of styryl compounds which I have foundwill act as supersensitizers for pseudocyanines and which class may bedefined as dialkylamino styryls which contain a heterocyclic nitrogencontaining nucleus or ring which latter may be substituted, if desired,so long as such substitution does not destroy the power of the styryl toseparately sensitize a photographic emulsion; I regard a fused-onbenzene ring as being within the foregoing definition, as for instancein the case of a quinoline or benzothiazole nucleus.

These examples also illustrate that, as basic sensitizers, thepseudocyanines all appear to be susceptible of being supersensitized bythe class of styryls described. It willbe noted that these 7;) maycontain a nucleus containing either sulphur or selenium or may containmerely a quinoline nucleus. They are further characterized in that thosepseudocyanines most readily susceptible to supersensitizing, have asharp 75 peak or maximum in their region of spectral sensitivity. Whilethe nuclei of these pseudocyanines may be substituted as illustratedabove, too heavy a substitution may result in a pseudocyanine which willnot respond notably to supersensitization as in the case, for instanceof 1 methyl 1' ethyl 6 dimethylamino pseudocyanine iodide.

The basic structure and source of the basic sensitizers and thesupersensitizers above named are well known to those skilled in the art,either being set forth in the published literature, or in availablepatents, so that the description of their methods of preparation isunnecessary.

Other examples showing the broad application of my invention could becited but the foregoing will be sufiicient to teach those skilled in theart, the manner in which my invention is carried out and the broadprinciple of supersensitizing basic sensitizers of numerous types withcompounds which themselves have separate sensitizing properties and theregions of sensitivity of which coincide at least in part with therespective regions of sensitivity of the basic sensitizers.

Numerous variations to the above invention will doubtless occur to thoseskilled in the art and will be included in the scope of my invention asdefined by the claims appended hereto, it being understood that theforegoing is merely illustrative of the manner of practicing myinvention and the results to be obtained thereby.

What I claim as my invention, and desire to be secured by Letters Patentof the United States is:

1. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a pseudocyanine, as a basic sensitizer, andthe other of which is, as a supersensitizer, a dialkylamino styrylderivative of an alkyl quaternary salt of a simple nitrogen-containingheterocyclic base.

2. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a pseudocyanine, as a basic sensitizer, andthe other of which is, as a supersensitizer, a dialkylamino styrylderivative of an alkyl quaternary salt of a simple nitrogen-containingheterocyclic base which base carries as substituents, alkyl groups oralkoxy groups or a fused-on benzene ring.

3. A gelatino-silver-halid'e emulsion containing two sensitizers for theemulsion, one 01' which is, as a basic sensitizer, a pseudocyanine whichpossesses a relatively sharp maximum in its region of spectralsensitivity, and the other of which is, as a supersensitizer, adialkylamino styryl derivative of an alkyl quarternary salt of a simplenitrogen-containing heterocyclic base.

4. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is, as a basic sensitizer, a. pseudocyanine whichpossesses a relatively sharp maximum in its region of spectralsensitivity and the nuclei of which do not carry a dialkylamino group asa substituent, and the other of which is, as a supersensitizer, adialkylamino styryl derivative of an alkyl quaternary salt of a simplenitrogen-containing haterocyclic base.

5. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a thiopseudocyanine, as a basic sensitizer,and the other of which is, as a supersensitizer, a dialkylamino styrylderivative of an alkyl quat nary salt-of a simple nitrogen-containingheterocyclic base.

6. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a selenopseudocyanine, asa basic sensitizer,and the other of which is, as a supersensitizer, a dialkylamino styrylderivative of an alkyl quaternary salt of a simple nitrogen-containingheterocyclic base.

I. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a lzl'dialkyl pseudocyanine halide, as a basicsensitizer, and the other of which is, as a super sensitizer, adialkylamino styryl derivative of an alkyl quaternary salt of a simplenitrogen-com taining heterocyclic base.

8. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a 1:1 dialkyl pseudocyanine halide, as a basicsensitizer, and the other of which is pinafiavol as a supersensitizer.

9. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is 1:1 diethyl pseudocyanine iodide, as a basicsensitizer, and the other of which is, as a supersensitizer,a'diaikylamino styryl derivative of an alkyl quaternary salt of simplenitrogen-containing heterocyclic base.

10. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a 6 alkyl 1:1 dialkyl pseudocyanine halide, asa basic sensitizer, and the other of which is pinaflavol as asupersensitizer.

11. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is 6 methyl 1:1 diethyl pseudocyanine iodide, asa basic sensitizer, and the other of which is pinafiavol as asupersensitizer. I

12. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is a 4 aryl 3:1 dialkyl thiazolo pseudocyaninehalide, as a basic sensitizer, and the other of which is pinaflavol as asupersensitizer.

13. A gelatino-silver-halide emulsion containing two sensitizers for theemulsion, one of which is 4 phenyl 3:1 dimethylthiazolo pseudocyanineiodide, as a basic sensitizer, and the other of which is pinaflavol as asupersensitizer.

14. A photographic element comprising a gelatino-silver-halide emulsioncontaining two sensitizers for the emulsion, one of which is apseudocyanine, as a basic sensitizer, and the other of which is, as asupersensitizer, a dialkylamino styryl derivative of an alkyl quaternarysalt of a simple nitrogen-containing heterocyclic base.

15. A photographic element comprising a gelatino-silver-halide emulsioncontaining two sensiti'zers for the emulsion, one of which is, as abasic sensitizer, a pseudocyanine which possesses a relatively sharpmaximum in its region of spectral sensitivity, and the other of whichis, as a supersensitizer, a dialkylamino styryl derivative of an alkylquaternary salt of a simple nitrogen-containing heterocyclic base.

CHARLES E. MEES.

